Distribution of Phytophthora and Pythium species in soils in the Continental United States

Abstract

The Pythium flora of 2132 soil samples from all sections of the United States was determined using an apple trapping method and two selective media. Isolates of the P. irregulare – P. debaryanum complex were obtained from 90% of the samples, and made up 55% of the 10 566 isolates examined. Isolates referable to the P. dissotocum – P. perniciosum complex, P. spinosum, P. splendens, P. ultimum, P. vexans, and heterothallic forms including P. sylvaticum, P. heterothallicum, and P. intermedium were obtained from 5 to 15% of the samples. Pythium afertile, P. aphanidermatum, P. dissotocum – P. perniciosum, P. irregulare – P. debaryanum, P. spinosum, P. torulosum, P. ultimum, and the heterothallic species were found in soil samples from 60% or more of the sections of the country sampled. The following species were isolated infrequently: P. acanthicum – P. oligandrum complex, P. catenulatum, P. helicoides – P. oedochilum complex, P. mamillatum, P. middletoni, P. myriotylum, P. paroecandrum, P. periplocum, P. prolatum, P. pulchrum, P. rostratum, P. vexans, Phytophthora cinnamomi, and P. parasitica.

Bait method to detect Pythium species that grow at high temperatures in hydroponic solutions

“…It is therefore vitally important to develop disease management strategies that include the monitoring of high-temperature Pythium species in recirculating hydroponic culture systems. Pythium and Phytophthora species can be captured in soil using a variety of plant materials as baits (Hendrix and Campbell 1970;Sanchez et al 2000;Thinggaard and Andersen 1995;Watanabe 1981Watanabe , 1984. For example, Thinggaard and Andersen (1995) found that zoospores of Phytophthora cryptogea Pethyb.& Laff.…”

“…Baiting methods have traditionally been used to isolate Pythium and Phytophthora species from soil (Hendrix and Campbell 1970;Matsumoto and Sato 1979;Watanabe 1984). However, there have been few reports on baiting methods to detect zoosporic pathogens in hydroponic solutions.…”

A review of southern pine decline in North America

“…Pythium spp. fungi, implicated as factors in littleleaf disease (Lorio, 1966;Hendrix and Campbell, 1970), are often associated with P. cinnamomi (Otrosina and Marx, 1975). Armillaria mellea (Vahl) P.…”

Distribution and populations of Pythium species in the northern and southern parts of Japan.

“…have been studied with emphasis on their isolations, distribution, and population dynamics in relation to the forest nursery diseases and bean disease complex in the United States and other countries1, 2,3,5,6,7,8) Although considerable knowledge on the seedling diseases of various plants caused by Pythium spp. has recently been accumulated in Japan, only a few reports have been available on their ecology.…”